Rozhen Observation Calendar

Which nights are best for a target over the coming weeks. The astronomy mark (darkness × altitude × Moon) is computed for every night; the weather and the overall mark exist only where Open-Meteo has a forecast (the next four days) or ERA5 history (past nights) — the rest is honestly blank.

Best nights for Great Orion Nebula: 01-23 (89), 01-24 (89), 01-25 (89), 01-26 (89), 01-27 (89) — by astronomy; check the weather when the night is within four days.

2028-01-23astronomy score per night — click a bar for that night2028-02-21

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2028-01-23 Sun	89	—	unknown	19:05–01:05 (good, 6.0 h)	42.9° 21:45	11.04	7%	147.1°
2028-01-24 Mon	89	—	unknown	19:05–01:00 (good, 5.92 h)	42.9° 21:45	11.01	3%	142.7°
2028-01-25 Tue	89	—	unknown	19:05–01:00 (good, 5.92 h)	42.9° 21:40	10.99	0%	135.7°
2028-01-26 Wed	89	—	unknown	19:05–00:55 (good, 5.83 h)	42.9° 21:35	10.96	0%	127.3°
2028-01-27 Thu	89	—	unknown	19:10–00:50 (good, 5.67 h)	42.9° 21:30	10.93	2%	118.1°
2028-01-28 Fri	89	—	unknown	19:10–00:45 (good, 5.58 h)	42.9° 21:25	10.9	5%	108.5°
2028-01-29 Sat	89	—	unknown	19:10–00:45 (good, 5.58 h)	42.9° 21:25	10.87	10%	98.5°
2028-01-30 Sun	89	—	unknown	19:10–00:40 (good, 5.5 h)	42.9° 21:20	10.84	16%	88.5°
2028-01-31 Mon	87	—	unknown	19:15–00:35 (good, 5.33 h)	42.9° 21:15	10.81	23%	78.4°
2028-02-01 Tue	83	—	unknown	19:15–00:30 (good, 5.25 h)	42.9° 21:10	10.77	32%	68.3°
2028-02-02 Wed	72	—	unknown	19:15–00:10 (good, 4.92 h)	42.9° 21:10	10.74	41%	58.4°
2028-02-03 Thu	56	—	unknown	20:10–23:55 (good, 3.75 h)	42.9° 21:05	10.71	51%	48.9°
2028-02-04 Fri	39	—	unknown	19:15–00:45 (marginal, 5.5 h)	42.9° 21:00	10.67	62%	40.4°
2028-02-05 Sat	25	—	unknown	19:20–00:25 (marginal, 5.08 h)	42.9° 20:55	10.64	72%	34.1°
2028-02-06 Sun	15	—	unknown	19:20–23:55 (marginal, 4.58 h)	42.9° 20:50	10.6	81%	31.9°
2028-02-07 Mon	13	—	unknown	19:20–20:55 (marginal, 1.58 h)	42.9° 20:50	10.57	90%	35.2°
2028-02-08 Tue	16	—	unknown	19:20–22:10 (marginal, 2.83 h)	42.9° 20:45	10.53	96%	42.9°
2028-02-09 Wed	23	—	unknown	19:25–23:35 (marginal, 4.17 h)	42.9° 20:40	10.49	99%	53.5°
2028-02-10 Thu	35	—	unknown	19:25–23:55 (marginal, 4.5 h)	42.9° 20:35	10.46	100%	65.6°
2028-02-11 Fri	50	—	unknown	19:25–21:35 (good, 2.17 h)	42.9° 20:30	10.42	97%	78.3°
2028-02-12 Sat	80	—	unknown	19:25–23:15 (good, 3.83 h)	42.9° 20:30	10.38	92%	91.0°
2028-02-13 Sun	87	—	unknown	19:25–23:25 (good, 4.0 h)	42.9° 20:25	10.34	84%	103.5°
2028-02-14 Mon	89	—	unknown	19:30–23:30 (good, 4.0 h)	42.9° 20:20	10.3	75%	115.3°
2028-02-15 Tue	89	—	unknown	19:30–23:35 (good, 4.08 h)	42.9° 20:15	10.27	65%	126.2°
2028-02-16 Wed	88	—	unknown	19:30–23:30 (good, 4.0 h)	42.9° 20:15	10.23	54%	135.7°
2028-02-17 Thu	86	—	unknown	19:30–23:30 (good, 4.0 h)	42.9° 20:10	10.18	44%	143.1°
2028-02-18 Fri	84	—	unknown	19:35–23:25 (good, 3.83 h)	42.9° 20:05	10.14	34%	147.4°
2028-02-19 Sat	82	—	unknown	19:35–23:20 (good, 3.75 h)	42.9° 20:00	10.1	25%	147.7°
2028-02-20 Sun	80	—	unknown	19:35–23:15 (good, 3.67 h)	42.9° 19:55	10.06	17%	144.0°
2028-02-21 Mon	80	—	unknown	19:35–23:10 (good, 3.58 h)	42.9° 19:55	10.02	10%	137.6°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2028-01-23&days=30"
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&days=30&format=csv" -o m31-calendar.csv

One row per night: score_astronomy always, score_weather / score only where a forecast or history exists (null otherwise, with weather_source saying which), best window, dark hours, Moon illumination and separation, transit. 7–60 nights. Errors: 400 with invalid_date or target_unresolved. Results are cached for six hours; calculation version 2026-10-10.1.